>Furigana codes would simply mark certain text as furigana, meaning to
>the text-display device, "These characters are not to be displayed on
>the main line of text, but rather above it and in smaller type". There
>ought to be <furi kana="...."> and </furi> codes, or the equivalent,
>in HTML; at least that is my opinion. The tag <furi kana="...."> would
>indicate the start of the characters that the furigana is to be placed
>over. The input kana="...." would tell the browser what the kana are.
>The </furi> tag would indicate the end of the characters to be given
>furigana.

I'm presuming, from your description, that Furigana is another term for
Ruby. There is a <ruby> OpenType layout feature, which will be published
with the next version of the OpenType spec, and this provides font support
for Ruby/Furigana text. I think it would be the responsibility of
application and markup language developers and standards bodies to decide
how to tag this kind of text, and obviously such tagging could work with
the OT feature in line layout and glyph positioning.

Note that this is a text tagging issue, not a Unicode issue, unless you
feel that there is some need to indicate Ruby/Furigana in plain text. At
some point, plain text ceases to be plain if you decide that layout
information needs to be encoded.